The addition of a group that does not use the drink additive but adds a similar-looking substance that they think is the additive would dr. bloedorn address what threat to internal validity?

The similar looking substance is acting as a placebo. In other words, a substance that will not have any therapeutic effects on the patient.

A placebo is currently used in the treatment of people with hypochondria, which is a psychological condition in which a person is under a constant belief that he or she is having an illness.

By adding this alternative substance (or placebo), Dr. Bloedorn is trying to address the individual's condition of hypochondriasis.

answer; i believe the answer is 80%, plz check first good luck;